Cocos2DMain PageBug list / Feature listRepository
Summary: Cocos2D is a framework that takes out most of the complications and lower level routines needed to write successful 2D games. It is not a substitute for programming as you will still require a very fundamental knowledge of Objective-C if you wish to progress further with it. It also supports tons of freeware/shareware projects to help assist you in rapid development such as:

To begin with these are the ones that I know of (in alphabetical order):

Cocoas2D – 2D Game Engine, Open Source, LGPL
iTGB for 2D Games – 2D Game Engine, Commercial, Min. cost $500
OOlong Engine – 3D Game Engine, Open Source, MIT License
SIO2Engine – 3D Game Engine, Open Source, Payment or flash screen on game required
Ston3D for Iphone – 3D Game Engine, Commercial, Min. cost approx. $250 (based on current conversion rates)
Unity3D Engine – 3D Game Engine, Commercial, Min. cost $199 + $399 If you have any exprience using any of the above engines in development please post any opinions you have. If you know of any other 3D or 2D Headache Behind Eyes

Corona SDK - Now available for Windows and Mac, free unlimited trial, only pay when you're ready to submit to the App Store or Android store (yes, it's cross-platform). http://www.anscamobile.com/corona/

Someone also mentioned iTGB from GarageGames as being $500 -- that's the old price. GG was sold and the new owners are charging $99 each for Torque 3D, Torque Game Builder, and iTorque Game Builder.

I'm working on Kobold2D (http://www.kobold2d.com), an improved version of Cocos2D featuring a lot more sample code, much better documentation and a serious effort to improve cross-platform (iOS & Mac OS) support.

I also want to provide a much more streamlined experience for beginning developers, starting with an installer, tools to create new projects from the 15+ template projects and upgrading projects to newer versions of Kobold2D is also just a mouse-click. API improvements are made to make programming games easier, for example KKInput significantly simplifies how you work with user input states (keyboard, mouse, accelerometer, gyroscope, touches and gestures).